1. Field of Invention
The invention relates to a sewing machine capable of changing a needle position and, in particular, to a sewing machine where a desired seam allowance width can be set and indicated on the display.
2. Description of Related Art
In conventional electronic controlled zigzag sewing machines, a needle is provided that is fixed movably in a lateral direction perpendicular to a feed sewing direction and a feed dog that enables a work cloth to be moved in the feed direction, a stepping motor for swinging the needle via a swinging mechanism, and a stepping motor for driving the feed dog via a linked material feed mechanism. The sewing operation is performed by driving the stepping motors both for swinging and driving to control the vertical movement of the needle bar based on zigzag width data and feed pitch data, respectively, stored in sewing patterns, such as straight patterns and zigzag patterns, which can be selected.
For example, when a patchwork quilt is made by joining together a plurality of small work cloths, or pieces, using a straight pattern sewn at a designated seam allowance of, for example, 7 mm away from the edges of the work cloths, the straight pattern needs to have been previously copied on to each of the work cloths, or pieces, to be sewn using a writing utensil, such as a French chalk, to provide a designated seam allowance. If a scale is indicated on the top of the machine bed, a seam allowance can be easily identified using the scale. Therefore, it is easy to mark a desired seam allowance on the edges of the work cloths, or pieces, at designated distances using a writing utensil, such as the French chalk.
On the other hand, another conventional zigzag sewing machine is disclosed in U.S. Pat. No. 4,876,977. In the disclosed machine, when a zigzag pattern is selected, a zigzag width and a stitch length for the zigzag pattern are displayed on the display. Then, when a straight pattern is selected, a distance from a predetermined reference position (e.g., left end or center) in a lateral long needle hole of the presser foot to a needle penetration position is displayed on the display.
In either case mentioned above, however, a distance from an absolute position to a needle penetration position, that is, a seam allowance is not easily obtained.
As described above, when a pattern is sewn, it is not easy to find a seam allowance, therefore, the line for the seam allowance needs to be marked at the edge of a work cloth to be sewn using a writing utensil, such as a French chalk, before sewing. To make a large-sized patchwork quilt, where a plurality of small cloths, or pieces, are joined together at a designated stitching position from each edge, takes a long time and it is a heavy burden to mark the pattern on the work cloths, or pieces, and a great deal of French chalk is wasted, which leads to a higher material cost.